Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - 1979 Volvo 264 2.66 liter V6 idle problem
View Single Post
  #10 (permalink)  
Old 08-06-2010, 02:27 PM
WW2dude WW2dude is offline
Registered User
 
Last photo:
Join Date: Jul 2006
Location: Paradise, CA
Age: 24
Posts: 17
Wiki Edits: 0

Thanks: 0
Thanked 0 Times in 0 Posts
Thanks to everyone for the help. That PDF may come in handy, thanks Latech. I'm going to check everything I can that's been suggested. I think I may have found the problem today, but first: I checked the cold start injector. I ran the car until it had problems idling and then disconnected the power to it. It made no difference, so I don't think it's spraying too long. I think I've tracked down every vacuum hose and replaced all that had cracks. I checked by hand The one I mentioned before that went to the air flow sensor from the auxiliary air valve. I couldn't see it, but I felt the rest of the hose that I couldn't see and it seems to be metal the whole way to the air flow sensor. It only uses a short rubber hose for the initial bend from the auxiliary air valve. That doesn't rule out a leak somewhere in there, it may have come loose, but I think it's unlikely.

Now to the interesting bit: The car has a single O2 sensor. It's a single-wire unheated type and thus takes awhile before it becomes active. I ruled this out as a cause of the problem before because:
A: The car started idling poorly before the O2 sensor should be active
B: I disconnected the power to the O2 sensor and it made no difference

Today i realized that ever since I cleaned that plugged up hole to the cold start injector, it runs much longer before it has a problem, and it may be heating up enough to make the O2 sensor a factor. So I ran it for about 4 minutes today, heating it up until the thermostat was about at the middle. At this point the car would not idle unless I revved it and released the peddle very gradually, and even then only some of the time. Once it was steady though, it would stay like that, until I revved it again. Then I revved it and released the peddle fast so that it started the usual up and down thing. I then quickly disconnected the power to the O2 sensor and the engine stabilized instantly. I repeated this multiple times. Sometimes, when the engine was stable and the O2 sensor disconnected, simply plugging it in would instantly cause it to bog down and up.

So, it looks like it may have been a combination of things, but I won't know for sure it's the only problem until I replace it. The manuals say the sensor should be replaced every 15,000 miles and I don't know when it was last replaced. The car has about 85,000 miles on it. I'm not going to stop here though, I'm going to continue checking things while I wait for a replacement.
Reply With Quote